Control system



Feb. 24, 1942.

W. F. SCANLAN CONTROL SYSTEM Filed March 26, 1941 v Waffen J'canZa/z Patented Felt. 24, 1942 z,z14,sa4 l comor. sysrarr Warren F. Scanlan, Chicago, 1li., assigner tov Charles?. Peirce, Chicago. 1li.

Application March 26, 1941, Serial No. 385.226

(Claims.

My inventionrelates, generally, to electric control systems and it has particular relation to burner control systems in which a burner in heating apparatus is initiated in operation an is controlled.

My invention is intended for use in controlling liquid fuel burners, commonly known as oil burners, vapor type burners and also gas type burners. 'I'he present invention will be described particularly in conjunction with an oil burner,

but it will be understood that it can be used g with other types of burners.

In the prior art of burner control a series of relays was used together with mercury switches and various thermal units. Because of the characteristics and dependency of thermal metals on changing temperature, instantaneous control was not feasible due to the fact that these metals require for their actuation substantial changes in temperature, and, therefore, they are subject to considerable time delay. In many instances this time delay is variable and often extends over a period of several minutes. Even with the finest adjustments that are allowable a ilve second time delay is required before the control can become effective.

In burner control systems of the prior art employing light sensitive cells or photo cells for detecting the presence or absence of flame on the burner there has been the serious objection that if the photo cell circuit becomes short cirv cuited fuel continues to be supplied to the burner even though the flame may have been extinguished. One of the objects of my invention is to prevent the further supply of fuel to a burner in the event that the photo cell circuit becomes short circuited.

Another object of my invention is to permit the supply of fuel to a burner on which the flame burns intermittently for a predetermined interval and which will prevent the further supply of fuel to the burner if the intermittent operation of the flame does not cease before the end of the interval.

A further object of my invention is to provide for locking out a burner control system in the event that the flame is not established a predetermined time after a cycle of operations intended to result in-establishment of the flame is initiated.

A still further object of my invention is to provide for locking out the burner control system if the electric valve employed in the system fails or is removed, if the photo cell control circuit therefor becomes short circuited or if the flame burns intermittently for a predetermined interval as above set forth. l

Other objects of my invention will, in part, be obvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of my invention reference can be .had to the following detailed description taken i'n connection with the accompanying drawing in which the single ngure illustrates diagrammatically a concrete embodiment of my invention.

Referring now particularly to the drawing it will be observed that the reference character l0 designates, generally, a unit which may include an electro-responsive device or motor Il. The particular burner unit It illustrated diagrammatically is one of the oil type but it will be understood that the present invention is not limited to this particular type of burner. The motor I l, as is well known, forces the oil through the guns and nozzles of the burner. In a gas jtype of burner the electro-responsive means might be in the form of a solenoid operated valve or other similar means. The fuel is supplied from the burner I0 for combustion in a name as indicated at i2. For igniting the flame igniter electrodes Il are provided which are connected across a high voltage winding il of a transformer, shown generally at I5, having a primary winding I6 that is] arranged to be energized as will be hereinafter set forth.

If the burner had been one of the gas type there would be provision for a pilot ilame for igniting the gas from the burner. In such case it would be unnecessary to supply the igniter electrodes il.

In order to detect the presence or absence of the flame i2 a light sensitive device or photo cell Il is'provided in such position that the light rays from the name l2 can implnge thereon. As will be hereinafter set forth, the photo cell Il is employed for controlling the functioning of the electro-responsive device il.

The control of the burner system is initiated by a room thermostat indicated at 20. It will be understood that the room thermostat Il will be located in a position which fairly represents the temperature of the space that is to be heated by the burner I0. It may be of various types. For convenience a room thermostat of the bimetallic type is illustrated but it will be understood that other types of similar control devices can also be employed.

The room thermostat 2l is arranged to complete the energization of a control circuit from a secondary winding 2i of a transformer, shown generally at 22. The transformer 22 comprises a primary winding 23 which is connected through a manually operable switch 24 for energization to `a suitable source 25 of alternating current, such as a 60 cycle, 110 volt source.

The operation of the room thermostat 23 at a predetermined temperature is intended to effect the energization of an operating winding 21w of a tube control relay designated generally at 21. The relay 21 includes normally open contact members 21a and 21b which are arranged to be closed on energization of the winding 21w.

The closure of contact members 21a completes a circuit from a secondary winding 28 of the transformer 22 for energizing a filament 29 of an electric valve, shown generally at 30, of the gas filled type having an indirectly heated cathode 3|. The valve 30 also includes a control grid 32, a screen grid 33 and an anode 34.

The closure of contact members 21h completes a circuit through a winding 31w of a start relay shown generally at 31, to the screen grid 33. The start relay 31 is provided with normally open contact members 31a.

Connected in series circuit relation with the anode 34 is a Winding 38w of an auxiliary condition for resuming operation. The particular trol relay, shown generally at 33. The auxiliary control relay has normally open contact members 38a, A resistor 39 is connected in series circuit relation with the winding 38w for a purpose which will be described hereinafter.

The closure of contact members 38a of the auxiliary control relay 38 completes a circuit for energizing a Winding 4010 of a main control relay, illustrated generally at 40. lay 4D includes normally open contact members 40a and normally closed contact members 40h. It also includes normally open contact members 40e and normally closed contact members 43d.

A time delay relay, shown generally at 4i, is provided for taking care of certain intermittent operation of the flame I2. This relay is of the thermal type and it includes aA heater element 4 lr, a bimetallic element 41m and normally closed contact members 41a. The heater element 4|r The main control re-w is energized on closure of the contact members certain fault conditions a lock out time delay f relay, shown generally at 42, is provided. 'This relay comprises a heater element 42r and a bimetallic element 42m together with normally closed contact members 42a. The contact members 42a are connected in series circuit relation with the source 25 so that, when they are opened, the entire system is deenergized. An extension 43 is provided for the contact members 42a which has a hook portion 44 that is arranged to intert with a hook portion 45 that is stationarily mounted. A manually operable button 46 is provided for releasing the hook portion 44. It will be understood that once contact members 42a are opened, they are locked in the open position and that the manually operable push button 46 must be operated in order to permit reclosure of the contact members 42a. If desired the push button can be so mounted as to be inaccessible except to an authorized person who, before resetting the lock out time delay relay 42 would inspect the entire system to see that it is in proper conrthe igniter electrodes I3.

lock out mechanism shown is merely for illustrative purposes since it will be obvious that any suitable lock out mechanism can be 'employed for effecting the lock out function as previously set forth.

In describing the operation of the system shown in the drawing it will first be assumed that the contact members 42a of the lock out time delay relay are closed and that the room thermostat 2l is in the open circuit position. It will also be assumed that the manual control switch 24 is closed. Under these conditions the primary winding 23 of the transformer 22 is energized through the closed contact members 42a and the switch 24 from the source 25.

When the room thermostat is subjected to a predetermined temperature it will close and complete an obvious circuit for energizing the winding 21w of the tube control relay 21. The energizing current will also flow through the heater element 42r of the lock out time delay relay 42. 'I'his relay may be adjusted so that its contact members 42a will be opened only after the heater element 42r has been energized for a predetermined interval, such as one half minute. During this period certain control functions are completed which, if the system operates as intended, render the heater element 421' inetiective to open contact members 42a.

The energization of winding 21w of the tube control relay 21 closes contact members 21a to complete an obvious energizing circuit for the illament 29 of the electric valve 33. Contact members 21h are clod to vcomplete a circuit through the winding 3110 of the start relay 31 `to thescreen grid 33.

A predetermined timeJor example five seconds, after the contact members 21a and 21h are closed, suiilcient current iiows between the Vcathode 3l and the screen grid 34 to energixe winding 31w of the start relay 31 and close its contact members 31a.

The circuit for energizing the winding 31 can be traced from the sourceA 25 through conductor 5l, switch 24, conductor 5|, normally closed contact members 42a, conductor 52, contact members 21h, conductor 53, winding 31m, screen grid 33, cathode 3|, resistor 54, and conductors 55 and 5G back to the source 25.

The closure -of contact `members 31a of the start relay 31 completes circuit for energizing the electro-responsive device il and also the primary winding I5 of the transformer I5 for energizing The burner unit Il then is initiated in operation and, as soon as the fuel is discharged, it is ignited to form the iiame I2.

The circuit for energizing the electro-responsive device Il can be traced from the conductor 53, previously described as being energized, through contact members 31a, conductor 51, normally closed contact members 41a, normally closed contact members 4Gb, conductor 53, electro-responsive device Il, and conductors 53 and 55 back to the source 25. 'I'he circuit for energizing the primary winding I6 extends from the conductor 51 through normally closed contact members 40d, conductor 60, primary winding I6 and conductors 59 and 56 back to the source 25.

The closure of contact members 31a also effects the energization of heater element 4ir ot the time delay relay 4I. This circuit extends from the 'conductor 53, previously described as energized, through heater element 4|r and cons,av4,ss4

'doctors sa and u to tnesource n. 'rnc contact members la are delayed in opening for a time interval depending upon the adjustment of the relay. As` previously described. this time interval may be one minute.

As soon as the flame I2 appears light rays yfrom it impinge on the photo cell i1. It will be observed, that the photo cell il is connected by conductors l2 and Il for controlling the energization of the electric valve Il. It is connected by conductor l2 to control grid l2. By conductor it is connected to the commonconify the condition tends to persist, of course the nection Il between the winding to and the resistor Il. The purpose of this arrangement will be presently set forth. As soon as the electric valve 3l `isremiered conducting, winding Ilw of the auxiliary relay Itis energized and its contact members lia are closed.

The circuit for energizing the winding uw can be traced from'the conductor Il, previously described as energized, through resistor 3l, winding Ilw, anode Il, cathode Il, resistor B4 and conductors l5 and II to the source 2l.

Closure of contact members Ila completes an obvious energizing circuit forthe operating wind- '.ing |010 of the main control relay 40. Contact 'I'he continued energization of the heater element llr of the time delay relay Il will eiiect the opening of contact members lla. However, it is no longer necessary to maintain the circuit through these contact members for energizing the electro-responsive device ll under normal operating conditions and hence no functioning takes place at this time as'a result of opening of these contact members.

It will be observed that contact members a, which are closed on energization of the winding uw, are connected by conductors 65 and 6| to shunt the heater element 2r of the time delay lock out relay I2. Since this element is shunted in this manner it is ineective to cause movement of the bimetallic element 42m and opening of the contact members 42a.

When suflicient heat has been applied to cause the room thermostat 20 to be moved to the open position. operating winding 21u of the tube relay 21 will be deenergized. resulting in a deenergization of the start relay l1 and the electric valve I0. This further results in the deenergization of the windings uw and w of the auxiliary and main control relays 38 and II and subsequently the deenerglzation of the electro-responsive device i I. The system is then ready to perform the cycle of operatic just described when the room thermostat 20 a ain calls for heat.

It may happen that the oil supply for the burner I Il may become exhausted. When this occurs air is introduced into the fuel lines as well as sediment and other foreign substances. When the fuel supply is replenished, due to the fact that air is presentin the fuel line and also due to the possibility that there may be some sediment therein or because of cold weather'the system should be rendered inoperative.

It will be recalled that, as soon as light from the flame I2 impinges on the' photo cell I1, the

electric valve lll is rendered conducting and subsequently main control relay Il is operated. As soon as the ame I2 disappears, the electric valve Il is no longer conducting and the main control relay lll is deenergized. The circuit for energizing the electro-responsive device li then extends through the contact members lla of the time delay relay Il, as previously described. If

m the stuttering of the flame l2 continues for a fuel may not flow readily, there may be some time longer than the time for which the relay 4i is set, for example one minute, then at the expiration of this interval contact members lia are opened and when the main control relay l0 is deenergized. no energizing circuit for the electro-responsive device il is completed. Consequently, the electro-responsive device Il is deenergized and fuel is no longer supplied to the burner.

While the main control relay 40 has been intermittently operated in accordance with the presence or absence of the iiame I2, its contact members 40a have been intermittently short circuiting the heater element 2r of the time delay lock out relay 42. for eecting the opening of contact members Ila of time delay relay 4I the heater element 421' will be intermittently energized but not sumciently to eect operation of the bimetallic element 2m and opening of contact members `42a. When the main control relay I0 is finally deenergized because of the absence of the flame I2, the heater element 421' is energized for a time sumciently long to cause the bimetallic element 42m to open contact members 42a and operate the hook member M to the lock out position where a manual operation is required in order to restore the system to operative condition.

It is important to note that, if the conductors 02 and 63 which form the circuit interconnecting the electric valve l0 and the photo cell I1 are short circuited, relay 3l will be deenergized since the energizing current which previously flowed through the resistor l! and operating winding uw will then flow directly to the control grid 32 and not through the operating winding uw. Main control relay I0 will then be deenergized and consequently the electro-responsive device Il will be deenergized. The system will then be locked out as soon as heater element 2r has been heated suiilciently to eiect operation of the bimetallic element 42m to open contact members 42a. If the conductors 82 and 63 are short circuited while the room thermostat 20 is in the open circuit position nothing will happen. However, as soon as room thermostat 2l calls for heat the heater element 2r will vbe energized and, since main control relay Il under these assumed conditions cannot be energized, the bimetallic element 42m will be operated to open contact members 42a and lock out the system.

Of course if the electric valve 3|! is removed or if it fails to function it is not possible to effect During the period required energization of the auxiliary control relay 3l. Likewise it is not possible'to eect the energization of the main control relay Il and, if the room thermostat 20 should call for heat under these conditions, the system would be properly locked out.

Since certain further changes can be made in the foregoing system and ditierent embodiments of the invention can be made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawing and .described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A burner control system comprising, in combination, temperature responsive means; an electric valve including a cathode, a control grid, a screen grid and an anode; means controlled by said temperature responsive means for energizing said cathode on the occurrence of a predetermined temperature, electro-responsive means for controlling the supply of fuel to the burner, a start relay having an operating winding connected for energization to said screen grid and contact members disposed to be closed on energization of its winding, circuit means connecting said electro-responsive means for energization to a current source on closure of said contact members, means connected to said control grid for rendering said electric valve conducting as long as there is a flame on said burner, a main control relay having an operating winding connected to be energized as long as said electric valve is conducting and one set of contact members disposed to be opened and another set of contact members disposed to be closed on energization of its operating Winding, said sets of contact members being connected in parallel circuit relation with each other and in series circuit relation with said circuit means, and time delay means including normally closed contact members connected in series circuit relation with said one set of contact members and adapted to be opened a predetermined interval after the operating winding of said start relay is energized for thereafter preventing energization of said electro-responsive means when the flame on said burner intermittently appears beyond a limited extent during said predetermined interval.

2. A burner control system comprising, in combination, temperature responsive means; an electric valve including a cathode, a control grid, a screen grid and an anode; means controlled by said temperature responsive means for energizing said cathode on the occurrence of a predetermined temperature, electro-responsive means for controlling the supply of fuel to the burner, a start relay having an operating winding connected for energization to said screen grid and contact members disposed to be closed on energization of its winding, circuit means connecting said electro-responsive means for energization to a current source on closure of said contact members, means connected to said control grid for rendering said electric valve conducting as long as there is a flame on said burner, a main control relay having an operating winding connected to be energized as long as said electric valve is conducting and one set of contact members disposed to be opened and another set of contact members disposed to be closed on energization of its operating winding, said sets of contact members being connected in parallel circuit relation with each other and in series circuit relation with said circuit means, time delay means including normally closed contact members connected in series circuit relation with said one set of contact members and adapted to be opened a predetermined interval after the operating winding of said start relay is energized for thereafter preventing energization of said electro-responsive means when the ilame on said burner intermittently appears beyond a limited extent during said predetermined interval, and time delay lock out means initiated in operation by said temperature responsive means and adapted to be rendered ineifective by said main control relay on operation thereof for preventing subsequent control of the system by said temperature responsive means in the event that said time delay lock out means is not rendered ineii'ective during a predetermined interval after operation oi said temperature responsive means.

3. In a burner control system, in combination, temperature responsive means; an electric valve including a cathode, a control grid, a screen grid and an anode; means controlled by said temperature responsive means for energizing said cathode on the occurrence of a predetermined temperature, electro-responsive means for controlling the supply of fuel to the burner, a start relay having an operating winding connected for energization to said screen grid when said cathode reaches a predetermined operating condition and contact members disposed to be closed on energization of said winding for initially connecting said electroresponsive means for energization to a current source, control relay means for maintaining said electro-responsive means in energized operating condition, a resistor, circuit means connecting said control relay means for energization to said anode and through said resistor to a current source, a light sensitive device located so that light from the flame of said burner impinges thereon and connected between said control grid and the common connection between said control relay means and said resistor for maintaining said valve conducting as long as the flame persists, short circuiting of said light sensitive device effecting deenergization of said control relay means and of said electro-responsive means, and time delay means initiated in operation by said start relay for preventing subsequent initiation of the operation of said electro-responsive means by said start relay when the ilame on said burner intermittently appears beyond a limited extent during a predetermined interval after operation of said start relay.

4. In a burner control system, in combination, temperature responsive means; an electric valve including a cathode, a control grid, a screen grid and an anode; means controlled by said temperature responsive means for energizing said cathode on the occurrence of a predetermined temperature, electro-responsive means for controlling the supply of fuel to the burner, a start relay having an operating winding connected for energization to said screen grid when said cathode reaches a predetermined operating condition and contact members disposed to be closed on energization of said winding for initially connecting said electroresponsive means for energization to a current source, control relay means for maintaining s'aid electro-responsive means in energized operating condition, a resistor, circuit means connecting said control relay means for energization to said anode and through said resistor to a current source, a light sensitive device located so that light from the ame of said burner impinges thereon and connected between said control grid and the common connection between said control relay means and said resistor for maintaining said valve conducting as long as the-name persists, short circuiting of said light sensitive device effecting deenergization of said control relay means and of said electro-responsive means, time delay means initiated in operation by said start relay for preventing subsequent initiation of the operation of said electro-responsive means by said start relay when the flame on said burner intermittently appears beyond a limited extent during a predetermined interval after operation of said start relay, and time delay lock out means initiated in operation by said temperature responsive means and adapted to be rendered ineiective by said control relay means on operation thereof for preventing subsequent control of the system by said temperature responsive means in the event that said time delay lock out means is not rendered ineffective during a predetermined interval after operation of said temperature respon- 10 sive means.

WARREN F. SCANLAN. 

